With the development of communications technologies, green communications has become a trend. How to reduce transmit power of a base station without affecting system performance has great significance for operators to reduce operating costs.
A channel capacity formula commonly used in communications technologies is expressed as formula (1).C=B·log2 (1+SINR)   Formula (1)where C is a channel capacity, B is bandwidth, and SINR is a signal to interference plus noise ratio. SINR is short for Signal to Interference plus Noise Ratio, and in an environment with no interference, a signal to noise ratio SNR (Signal to Noise Ratio) may be used to replace the signal to interference plus noise ratio SINR.
Bandwidth is expanded to x times the bandwidth in a situation of same transmit power, as expressed by formula (2). The channel capacity may also increase accordingly. Therefore, if there is idle bandwidth, bandwidth scheduling and expansion may be used to reduce transmit power.
                    C        =                  x          ·          B          ·                                    log              2                        ⁡                          (                              1                +                                  SINR                  x                                            )                                                          Formula        ⁢                                  ⁢                  (          2          )                    
In the prior art, for long term evolution (LTE) terminals or other wireless communications devices, a method for reducing transmit power of a terminal by using bandwidth expansion is: first determining, by a terminal side, a requirement of a data transmission throughput of a mobile terminal and path loss information of data transmission; selecting a combined transmission parameter for bandwidth expansion based on the requirement of the throughput and the path loss information; and readjusting transmit power of the terminal, so as to reduce the transmit power of the terminal. In this process, a behavior of a base station is cooperating with the terminal side.
However, by using the foregoing bandwidth expansion manner, only the transmit power of the terminal is reduced, and transmit power of a base station side is not affected.